Hydraulic drive unit



Feb. 19, 1946. G. E. THOMPSON 2,395,355

, HYDRAULIC DRIVE UNIT Filed Aug 28,1943 2 Sheets-Sheet 1 INVENTOR G'eaE', Thom 5 on Feb. 19, 1946. THOMPSON 2,395,355

HYDRAULIC DRIVE UNIT Filed Aug. 28, 1943 '2 Sheets-Sheet \j INVENTOIR Geo. E Thompson BY F7 TTYS Patented Feb. 19, 1946 UNITED STATES PATENT OFFICE 2,395,355 HYDRAULIC DRIVE UNIT f George E. Thompson, Stockton, Calif. Application August 28, 1943, Serial No. 500,355

Claims.

This invention relates to a hydraulic drive mechanism, my principal object being to provide a unit of this character particularly adapted for motor vehicle use, which eliminates the need of a clutch and which, when coupled together as a pair in a certain manner, takes the place of the usual differential mechanism, as well as a clutch.

Another object is to provide a unit of this nature which is small and compact for the power developed, and thus is capable of being mounted in direct connection with each wheel of the vehicle within the brake drum, thus givingan individual difierentiated drive for each wheel to which the unit is applied and without increasing the size of the brake drum and other adjacent standard size parts. l A further object is to construct the unit in such a manner that the oil pressure developed with the operation of this unit is confined within the body of the unit, only in certain small areas thereof. Thus, while the unit is necessarily enclosed in an oil retaining housing, suchhousing does not require pressure tight packings about the rotating members connected to the unit and which project from the housing.

The unit is also so constructed that Wear is reduced to a minimum, so that the unit will give long and eificient service without repair or replacement of parts being necessary.

'A further object of the invention is to produce a simple, inexpensive device. and yet one which will beexceedingly effective for the purpose for which it is designed.

These objects I accomplish by means of such structure and relative arrangement .of parts as will fully appear by a perusal of the following specifications and claims.

In the drawings similar characters of reference indicate correspondingparts in the several views:

Figure l is a side elevation of my improved unit with the driving or driven member detached therefrom and partly in section to show the pumping mechanism, the pump plungers and flow control valves being in their outermost position.

Figure 2 is a fragmentary sectional elevation showing a flow control valve at its inner position.

Figure 3 is a side elevation of the unit showing the pump plungers at their inner position and manually activated means to depress the flow control valves.

Figure 4 is an end view of a pair of the units as connected and mounted for use as a difier: ential mechanism in a motor vehicle.

Referring now more particularly to the numerals of reference on the drawings, the unit comprises a cylindrical disc like body I, having a central opening 2 of considerably larger size than the axial shaft 3 which projects into the opening.

Formed in the body are a number of radially disposed cylinders 4 which are grouped evenly about the body. The cylinders are initially open at both ends, to the opening 2 and to the outer periphery of the body, being closed at thelatter end by plugs 5. A tubular plunger 6 is mounted in each cylinder, each plunger at its outer end being formedwith a valve seat I normally engaged by a ball check valve 8 which is held against the seat by a light tension spring 9. The plunger is yieldably depressed in the cylinder (or advanced toward the opening'2) by a compression spring l0 disposed between the outer end of the plunger and the plug 5. This spring is stronger than tension spring9 and is disposed so that it does not interfere with the valve movement.

Disposed alongside each cylinder 4 is a cylindrical passage II extending through the body through the opening 2 to its outer periphery and formed intermediate its ends with an annular shoulder l2 facing away from the opening 2. A flow-control plunger type valve I3 is slidable in the passage H radially out from the shoulder I2 and. projecting from the periphery of the body with a preferably rounded head 14 on its outer end. The inner end of the valve is formed as a fiat surface 5 to closely seat against the shoulder 12. The valve is normally advanced radially out so that the surface l5 clears the shoulder H a considerable distance by a compression spring I6 within the passage ii.

Intermediate its ends the valve 13 isiormed witha pair of circular axially spaced grooves l1 and 18 of gradually increasing depth so as to form abrupt shoulders IS on one side facing radially out. Between the inner groove l1 and the surface I5 the valve is cut down along its periphery to form an oil escape passage 20. The land 2| between the grooves, however, closely fits the passage ll.

A port 22 is cut in the body I to establish com munication between each cylinder 4 and the corresponding passage II. This port is so positioned that its cylinder end is radially out from the plunger 6 when the latter is in itsoutermost position, while the other end of the'port registers with the groove I! when the valve I3 is in its outermost position as shown in Figure 1. The

space between the grooves H and I8 relative to the possible depressing movement of the valve 13 from its outermost position is such that when the valve surface l seats against the shoulder L2, theport 22 registers with the outer groove 18 as shown in Figure 2.

To move the plungers radially out against the resistance of the springs ID, a star cam 23, having as many points as there are plungers, is disposed in the opening 2 and is secured on the shaft 3. This shaft is journaled in the body on one side by means of a. ball bearing 24 thereon which is seated in a boss 25 projecting from the corresponding side of the body (see Figure 4),,

By reason of the above construction, -it will be 'seen that the plungers are simultaneously and successively depressed by the rotation of the cam relative to the body, forcing the plungers radially out against the spring resistance. When the plungers clear the cam points and are moved radially inward by the spring action, the ball checks fl-leave their seats "I, as shown in Figure 3, and admit oil into the cylinders radiallyout from theplungers from the interior of said plungers or from the opening -2. Upon outward movement of the plungers by the cam action, the balls become instant-ly-reseated and the oil is forced from the cylinder through the ports 22 into the grooves-l-l-of the valves 1-3. The oil then travels through the passages 20 back into the opening 2 and into the housing 26 which encloses the body and which is filled with oil at least to the level of the top-of opening 2. As long as the pumping speed, which depends on the relative speed of rotation of the body and shaft 3, does not exceed the carry-off capacity-of the passages 20, the body: and shaft may rotate relativeto each other. When however, therelative rotating speed is increased,thev'olume of oil being pumped into the cylinder is greater than the capacity of the passages 2-0. As a result, the oil becomes trapped in the cylindersthe plungers cannot move out to let the cam pass by the same and the shaftand the body rotate together. The raster the initial relative speed of rotation of theparts, the quicker and more effective will be this driving action and the slippage between the body-and-s'hait will be v correspondingly lessened.

'As the pressure within each cylinder increases and [builds up, such pressure-acts against the shoulder I 9 of-each va'lv-e groove I 1 and" tends to force the valve radially inward against the resistance ofthe spring 16. This in turn tends to move the land 2 "across the port 22 and thus formsa positive closure, preventing escape of the oil "from the cylinder. It will "be noted that only the outer portions'ofthe cylinder and the ports 22 are the pressure areas of the entire "In order to shift the valve -l3 alltheway-in so that the oil pressure will pass into the groove 1-8 fromthe ports -2-2 and thus positively prevent escape of oil fromthe cylinder except'for-any small leakage, I provide a flexible controlband 21 disposed in the housing "26 about and in line with the valves -|3, 'as shown in-Figure 3. This band has separated ends similar to a brake band and which ends are connected to a rocking arm 28 mounted in the housing. This arm is adapted to be turned in a direction to cause the bandto contract about the body and depres the valves 1-3 by suitable means such as a pull lever -29 di's posed-"outside the housing and connected to the V the contracting pressure on the band may be released since the oil pressure acting against the shoulders I9 of the grooves l8 prevents outward movement of the valves until the pressure becomes relieved by a relative reduction of speed of the body or shaft sufficient to enable the springs 16 to push the valves I3 out. By this ciable length, and the plungers at their inner end -or within the opening 2 are correspondingly spaced. In order to cushion the rotation of the cam as the points leave each plunger and before picking up the next plunger, and thus preventing a possible jerky movement, I provide another plunger '3'il, sli'dably mounted the body :between a pair ofiplungers 8. This plunger is mounted in :a radial bore 3l in the body and .is yieldably urged inwardly by compression spring-'32. 13y reason of this cushion or shock absorberiplunger 30, which is advanced into the opening Y 2 when the adjacent vplungers 'fi are depressed, the sudden release of the cam after the points simultaneously leave the plungers '6, .is cushioned and the cam is prevented from ujer y :or unevenzrotation. It will be noted that plunger 30 is also tubular, the :bore being substantially butnot perfectly closed by a ball check 37 duringoutwardmovement of theplunger. This provide aire'sistance against such outward movement, in addition to the spring pressure, and allows of a fast'linward or return movement. 7

Either the body, itself, 'or "the-shaft 3., serves as a 'driving member :dependingeon the installation of the unit, For instance if the 'uni-tis mounted in a wheel on 'a motor vehicle,-the body is con-- nectedto-the wheel and the shaft forms thedrive member. If on the-otherjhandthe units-are arranged as a differential structure-and connected between a ,pair of wheel axleaas is commonpractice in motor vehicles, one-of the unit forms-the driving member and the-shaft 3, which aregthe ax1es,,become the driven members. ,Inthisrarrang-ement, the two units are connected-by sw'-table rigid ties 33; -and themain drive vgearfifl-is mounted on the body -of--'one unit. This :gear is engaged by a drive pinion 35,, the :units together with-the gear and pinion ibeingzenclosed in 56611" ventional form of housing 3&,.-which1the units and-axles are journaled as shown'inqFigure-n.

:From the vforegoing :description will --'be readily seen that I have; produced :a device as substantially fulfills theobjects of theinvention as :set forth herein.

Whilezthis specification sets -forthin :detailithe present and preferred construction of the sdevice, still practice such idG'ViEtiOIlS from such adetail may be resorted ito' asid'o not .formra, departure from :the spirit of. the invent-iomfas 'definezizby the appen'ded claiins. 1 Having thus described my invention, what 1 claim as new 'ancl useful and desire to Tsecure Fby Letter Patent is:

A hydraulic drivennit bomprising aJr-o'tatable body, a shaft turnable mel'ative thereto, fa fixed housing about the body'auapted uto icon tain a supply of oil, the body having ia central opening about t'heshaft,- a cylinder in the body radial with I and opento said :opening: a tubular plunger slidablethe cylinderpa iihecki valveron the outer end of the plunger, a spring to move the plunger radially inward, a cam for the shaft to move the plunger radially out and mean in the body forming a restricted oil outlet from the cylinder to the outer surface of the body.

2. A unit as in claim 1, with means included with said last named means to increase the restriction and functioning upon a build up of oil pressure within the cylinder as induced by an initial relative high rotative speed of the body and shaft.

3. A hydraulic drive unit comprising a rotatable body, a shaft turnable relative thereto, a fixed housing about the body adapted to contain a supply of oil, the body having a central opening about the shaft, a cylinder in the body radial with and open to said opening, a tubular plunger slidable in the cylinder, a check valve on the outer end of the plunger, a spring to move the plunger radially inward, a cam for the shaft to move the plunger radially out, means in the body forming a passage adjacent the cylinder and open at one end to the outer surface of the body, a slide valve in said passage, a spring urging the valve in a direction away from the open end of the passage, the valve having a circumferential groove therein and the body having a port establishing communication between the cylinder outwardly of the plunger and the passage at a point in the latter to register with the groove when the valve is in its initial spring-urged position; the valve having a restricted passage from said groove to the end of the valve adjacent the open end of the passage.

4. A unit as in claim 3, in which the groove is of increasing depth from one side to form an abrupt shoulder on the other side Which faces in a direction away from the open end of the passage.

5. A unit as in claim 3, in which the valve is formed with another circumferential groove adapted to register with the adjacent end of the port when the valve is moved a predetermined distance in opposition to the spring.

6. A unit as in claim 3, in which the valve is formed with another circumferential groove adapted to register with the adjacent end of the port when the valve is moved a predetermined distance in opposition to the spring and manually controlled means to so move the valve.

7. A hydraulic drive unit comprising a rotatable body, a shaft turnable relative thereto, a fixed housing about the body adapted to contain a supply of oil, the body having a central opening about the shaft, a cylinder in the body radial with and open to said opening, a tubular plunger slidable in the cylinder, a check valve on the outer end of the plunger, a spring to move the plunger radially inward, a cam for the shaft to move the plunger radially out, means in the body forming a passage alongside the cylinder and open at one end to the central body opening, a slide valve in said passage, a spring urging the valve away from the open end of the passage, the valve having a circumferential groove therein and a restricted passage leading from said groove to the inner end of the valve; the body having a port establishing communication between the cylinder outwardly of the plunger and the passage at a point in the latter to register with the groove when the valve is in it initial spring-urged position.

8. A unit as in claim 7, in which the valve projects from the outer periphery of the body; and a manually activated member movable radially inward mounted in the housing in position to depress the valve when the member is thus moved whereby the groove will be shifted inwardly of the port and the latter closed.

9. A hydraulic drive unit comprising a rotatable body, a shaft turnable relative thereto, a fixed housing about the body adapted to contain a supply of oil, a pumping mechanism within the body to draw oil from the housing and return such oil to the housing thru a passage of restricted size, the body having a central opening into which the shaft projects and the pumping member including a pump plunger disposed substantially radially of the shaft and projectin into said opening, means to move the plunger radially inward, a cam on the shaft having a high point engageable with the plunger to move the same radially outward, a shock absorbing plunger slidably mounted in the body adjacent the pump plunger and projecting into the central opening into the path of the cam and yieldable means acting on said shock absorbing plunger moving the same radially inward.

10. A hydraulic drive unit comprising a rotatable body, a shaft turnable relative thereto, a fixed housing about'the body adapted to contain a supply of oil, a pump cylinder in the body, a plunger slidable in the cylinder, means to move the plunger in one direction, mean functioning upon such movement to draw oil into the cylinder from the housing, means forming a restricted oil outlet passage from the cylinder back to the housing, means to move the plunger in the other direction to force the oil through said passage upon relative rotation of the body and shaft, an element movable to close the passage, manual means to move such element, and means formed with the element to cause oil pressure within the cylinder to maintain the element in passage closing position once it is moved to such position.

GEORGE E, THOMPSON. 

